1. Field of the Invention PA1 2. Background Art
This invention relates to color photographic elements and in particular to color photographic elements capable of providing full color images with exposure of at least two silver halide emulsion layers to radiation outside the visible region of the electromagnetic spectrum. In particular, the present invention relates to a color photographic element having at least three emulsion layers associated with color image providing materials, each emulsion layer being sensitized to a different region of the electromagnetic spectrum and at least two layers being sensitized to radiation within the infrared region of the electromagnetic spectrum.
Dyes which have been capable of sensitizing silver halide emulsions to infrared regions of the electromagnetic spectrum have been known for many years. Merocyanine dyes and cyanine dyes, particularly those with longer bridging groups between cyclic moieties have been used for many years to sensitize silver halide to the infrared. U.S. Pat. Nos. 3,619,154, 3,682,630; 2,895,955; 3,482,978; 3,758,461 and 2,734,900; and U.K. Patent Nos. 1,192,234 and 1,188,784 disclose well-known classes of dyes which sensitize silver halide to portions of the infrared region of the electromagnetic spectrum. U.S. Pat. No. 4,362,800 discloses dyes used to sensitize inorganic photoconductors to the infrared, and these dyes are also effective sensitizers for silver halide.
With the advent of lasers, and particularly solid state laser diodes emitting in the infrared region of the electromagnetic spectrum (e.g., 780 to 1500 nm), the interest in infrared sensitization has greatly increased. Many different processes and articles useful with laser diodes have been proposed. U.S. Pat. No. 4,416,522, for example, proposes daylight photoplotting apparatus for the infrared exposure of film. This patent also generally proposes a film comprising three emulsion layers sensitized to different portions of non-visible portions of the electromagnetic spectrum, including the infrared. The film description is quite general and the concentration of imagewise exposure on each layer appears to be dependent upon filtering of radiation by the apparatus prior to its striking the film surface.